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There are
two basic types of televisions today, FLAT PANEL
and PROJECTION.
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There are two types of flat
panels, PLASMA and LCD.
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There are also two types of
projection, FRONT and REAR.
FLAT PANELS:
PLASMA- The plasma panel
is kind of a digital picture tube. Like the old fashioned picture tube it
uses phosphors which glow when turned on. The panel is built on a sheet of
glass. A very fine grid is bonded to the glass. Each box in the grid can be
turned on independently. These boxes have red, green, and blue phosphors.
The panel is filled with a special gas and topped with another glass
plate. If a pixel is turned on, the gas is
excited and that makes the phosphor glow.
Pros and cons:
The advantages of a plasma panel are the thin, flat design, a wide
viewing angle and excellent picture quality. A disadvantage of the
plasma is it’s very fragile. When moving the plasma, it is important to
keep the panel vertical. Any shaking while the panel is in a horizontal
position can break the seal between the glass panels and the grid. This
ruins the panel. The newest plasmas claim a long life expectancy and
improved resistance to image retention, which have been problems in
plasma televisions.
LCD –An LCD is also a
digital display. A light is shined through a grid of crystals. Each pixel*
can be turned on separately. A pixel is turned on to block the light.
Pros and cons:
The LCD panel also has a flat, thin design and is fairly light weight.
It is a little susceptible to image retention.
Since each pixel is naturally lit, LCD panels have difficulty creating a
black image. The new LCD panels have excellent picture quality over
all.
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PROJECTION:
Front Projection -This is
a separate unit, often ceiling mounted, which projects onto a screen. It is
common in commercial venues and high end home theater.
Rear Projection – Most
consumer large screen televisions are rear projections. There are four
types, CRT (picture tube), DLP, LCD and LCOS.
CRT -The CRT based
rear projection TV’s use 3 projection tubes. The three images reflect
off a mirror onto the screen.
Pros and cons: These
sets are large and heavy. The three images need to be converged
into one picture. These are almost extinct but do provide and
excellent picture quality.
DLP -The heart of the
DLP is the digital mirror device. A bright light is shined through a
color filter focused onto the digital mirror device. Each pixel is
represented by a mirror which is tilted one way to be on and the other
way to be off. The reflections are focused through a lens to the mirror
and onto the inside of the screen.
Pros and cons:
The DLP set gives an excellent picture quality, with a wide viewing
angle, but the lamp needs to be replaced after every several
thousand hours of operation. The DLP has no problem with image
retention.
LCD -A bright light
is divided into red, blue and green light. They are shined through LCD
panels, focused through a lens and onto a mirror, then to the screen.
Pros and cons:
The LCD gives an excellent quality picture, a good viewing angle,
and the black images are improving on the later sets. The lamp
will need to be changed after several thousand hours of operation.
LCOS –The LCOS is
similar to the LCD but the light is reflected rather than going through
the crystals.
Pros and cons:
The LCOS gives an excellent quality picture with really vibrant
color. The lamp needs to be replaced after several thousand hours
of operation.
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